October 15, 2010 at 7:45 am
Hi all,
Our company has been looking for a Senior level SQL Server DBA, and the last (2) candidates have been lacking some basic performance tuning skills. During our interview, we have a SQL trace that we captured from our production environment that we play back for the candidates. This playback provides a hands on assesment of the candidates ability to perform basic SQL Server 2008 R2 performance tuning techniques. Both of these candidates have over (7) years experience with SQL Server 2000/2005/2008.
What's been surprising, is that these "Senior" level candidates were not even aware of SQL Server's "Activity Monitor" and basic use of "SQL Server Profiler", or the use of DMV's. I'm a mid-level SQL Server DBA with about 4 years experience on SQL Server 2000/2005/2008, and I should not be teaching these techniques to "Senior" level candidates. I know there are third party tools to assist in performance monitoring, but I believe you should be able to utilize SQL Server's toolset's such as DMV's first. There will be times when these third party tools will not be available when the "poop" hit's the fan, so relying on them solely as your performance tuning method is a bad idea in my book.
Is this normal in the SQL Server DBA community?
😀
October 15, 2010 at 7:48 am
I have found similar, quite often 7 years experience = 7 x 1 year worth of experience.
But there a lot of excellent DBAs out there, its just a mattter of finding them..!
October 15, 2010 at 7:56 am
Performance tuning? I've had senior DBA candidates who couldn't tell me two types of SQL Server backups.
If I found a candidate that didn't know DMVs because he used a 3rd party tool I'd hire then in a second. I find more common they get the 'deer in headlights' look when the words 'performance monitoring' are event mentioned.
Yes, I'm in a cynical mood lately.
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability
October 15, 2010 at 8:02 am
Tim Parker (10/15/2010)
Is this normal in the SQL Server DBA community?
Not only in the SQL Server market - same happens with other RDBMS technologies.
Some DBA crown themselves "Senior" just because they have worked around databases for a few years - in some cases doing really basic stuff.
_____________________________________
Pablo (Paul) Berzukov
Author of Understanding Database Administration available at Amazon and other bookstores.
Disclaimer: Advice is provided to the best of my knowledge but no implicit or explicit warranties are provided. Since the advisor explicitly encourages testing any and all suggestions on a test non-production environment advisor should not held liable or responsible for any actions taken based on the given advice.October 15, 2010 at 8:06 am
well if we are trading war stories,
the last guy we interviewed we asked him how he would modify a query with a join to return all the rows from one table even if there were no matches, he fumbled around for 10 minute as it was apparent he was unaware of left-joins and even after a lot
of hinting from us, we told him to use a left-join and he still couldn't even work out the syntax!
this for a Senior SQL Dev.
October 15, 2010 at 8:08 am
I think the problem is that we don't have any rating of what a senior DBA is. Is it someone that's been a DBA for 7 years? Because it's easy to get to that point without straining your brain to solve problems. Or perhaps because you had a job where not a lot broke.
There are good DBAs out there, but hopefully they're quickly employed. If you find someone that doesn't know this stuff, do you consider them a mid-level DBA and pay them less? Or keep searching?
(moved to employees forum)
October 15, 2010 at 8:09 am
Time in job does not mean knowledgble. I interviewed a DBA with nine years of experience who did not know anything about user defined database roles or even that they existed. I did not hire him.
Experiences like this are why I conduct very in-depth technical interviews. Doesn’t mean they will work out if they pass the tech interviews, but at least it eliminates the weaker candidates.
October 15, 2010 at 8:18 am
Usualy a DBA does not work in "Project" mode, so once they start somewhere they usualy work there for some time (years).
So in the end finding a SQL DBA is not an easy thing and the good known ones are constantly busy.
You have to be a little bit lucky and have some kind of test to make sure they are really what they say (your test is a very good idea), being a sql DBA is very broad, even developer who worked with SQL Server could say he's a DBA just because he think he know some SQL statement.
On top of your test i would add the good old Fizz Buzz, ask them to tune a single query on 2-3 tables (with an index with an include or two missing), backup and restore a DB, create 100 Logins (to see if he can automate things), nothing that couldn't be done in less than 5 mins and look how they do it.
If the guy end up with a rbar solution for FizzBuzz it wouldn't be too bad but one that ends up with a set based solution will have a nice bonus on the final review.
Anyone doing a backup/restore with SSMS wizzard will have a (very) bad point (unless he uses it just to generate the script, then he's lazy -> good point).
Anyone opening the books online will have a good point.
Anyone creating more than 2 Logins without a script will have a bad point.
Anyone tuning the query by not looking at IO and Time statistics and query plan would immediately fail.
With that kind of test it's kinda easy to see if someone is used to work with SQL Server full time or if it's just a hobby.
October 15, 2010 at 8:23 am
I hate to use analogies here, but it's like auditioning a musician for a band. We can talk music theory all day, but if you can't play good music, you're no good to the band.
Thanks for all the replies, they're much appreciated.
😀
October 15, 2010 at 11:01 am
Sounds like a good interview technique. I prefer a hands-on approach to technical interviews over a "can he regurgitate BOL" technique.
And no, I'm not at all surprised about your results.
On the other hand, someone can be a very skilled DBA without being a skiller performance tuning expert. "DBA" covers WAY too much scope these days. Those 9-year vets might be experts at DR, architecture, security, even at CLR (.NET) coding, and be "senior DBAs" thereby, but not know about traces and such.
On your music analogy, would you refuse to hire a drummer because he doesn't know how to use a kettle drum, even though that might be the only drum on Earth he's not an expert at?
But, most likely, you're right. They've got no business calling themselves senior is the most likely answer.
- Gus "GSquared", RSVP, OODA, MAP, NMVP, FAQ, SAT, SQL, DNA, RNA, UOI, IOU, AM, PM, AD, BC, BCE, USA, UN, CF, ROFL, LOL, ETC
Property of The Thread
"Nobody knows the age of the human race, but everyone agrees it's old enough to know better." - Anon
October 15, 2010 at 11:04 am
Kettle drums are cool, they can be tuned to pitch.
😀
October 15, 2010 at 11:32 am
If a DBA works for a single organization for many years and never works outside that organization then they will only have the tools that are required by that job. So a DBA can conceivably work for 15 years and not know all the ins and outs of being a senior DBA, though they are titled a Senior DBA. If a DBA works a few years here and a few years there, acquiring the skills each unique experience affords then, as well as working with various other database professional, they learn to use a wider variety of SQL tools and master more of the techniques required to perform at a senior level.
October 15, 2010 at 11:39 am
GSquared (10/15/2010)
On the other hand, someone can be a very skilled DBA without being a skiller performance tuning expert. "DBA" covers WAY too much scope these days.
That's why I used to check CV for responsibilities before interview. If your CV states that you are a performance tuning specialist and don't know what an execution plan is or where to find it and have never heard of Profiler, there's a problem...
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability
October 15, 2010 at 11:42 am
GilaMonster (10/15/2010)
GSquared (10/15/2010)
On the other hand, someone can be a very skilled DBA without being a skiller performance tuning expert. "DBA" covers WAY too much scope these days.That's why I used to check CV for responsibilities before interview. If your CV states that you are a performance tuning specialist and don't know what an execution plan is or where to find it and have never heard of Profiler, there's a problem...
But Gail, I'm a performance tuning expert, and last I heard, profiling is politically incorrect.... :w00t:
- Gus "GSquared", RSVP, OODA, MAP, NMVP, FAQ, SAT, SQL, DNA, RNA, UOI, IOU, AM, PM, AD, BC, BCE, USA, UN, CF, ROFL, LOL, ETC
Property of The Thread
"Nobody knows the age of the human race, but everyone agrees it's old enough to know better." - Anon
October 15, 2010 at 11:42 am
That hits the nail on the head. I agree with you 100%.
I personally feel that I get discriminated against because of my time in grade as a SQL Server DBA. I have been exposed to a lot of facets in the world of SQL Server, and feel like I have a decent skill set. I've had a recruiter tell me that due to my 4 years experience, I did not posses the edge that the more seasoned (aka. 7+ years experience) SQL Server DBA's had. I told him to put me up against one of your seniors and I will show you what I can do.
I believe the industry as a whole may place too much emphasis on the years of experience, versus the actual aptitude of the individual they are interviewing. By putting the scenario exercise in place during the interview process, this bias can be erased from the industry.
In my little corner of the world, this has atleast been my experience.
😀
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